/usr/lib/x86_64-linux-gnu/libgnat-4.9.so is in gnat-4.9 4.9.3-3ubuntu5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgnat-4.9.so.1
/usr/lib/x86_64-linux-gnu/libgnat-4.9.so.1